This application in general relates to a mechanism for preventing leakage of gas flow across a valve/valve seat interface, and has particular application in the use of valves in regenerative incinerators.
Regenerative incinerators having a combustion chamber which communicates with several heat exchangers are known. Each of the heat exchangers serially receive cool "dirty" air to be cleaned which passes through the heat exchanger and into the combustion chamber and then hot "clean" air which leads from the combustion chamber through a second heat exchanger. A purge gas is a relatively clean gas typically driven through a heat exchanger which had previously been receiving cool air, to drive all "dirty" air from that heat exchanger before it switches to receiving the hot clean air. By alternatively passing cool air and then hot air through the heat exchanger, the heat exchangers are cyclically heated and cooled. The "dirty" air passing through the heat exchanger and into the combustion chamber is thus heated towards its ignition temperature prior to entering the combustion chamber. In this way, the efficiency of the combustion process is increased, and greater volumes of gas may be processed.
With prior art systems, each of the heat exchangers are cyclically in an inlet mode, a purge mode, and then an outlet mode. Complicated valving systems are necessary to properly communicate the heat exchangers to a source of dirty gas, to a downstream source for delivery of the clean gas from the combustion chamber, or to communicate a clean purge gas to the heat exchanger chamber. It is important that there be a minimal amount of leakage across any valve, since strict regulations control the amount of dirty gas which may enter the atmosphere.
It is known in the prior art to selectively communicate a pressurized gas to the interface between a valve seat and the valve disk to attempt to prevent the flow of leakage gas across the valve seat. Such prior art attempts have typically directed a small amount of pressurized gas perpendicularly into a groove at an intermediate location in a valve/valve seat contact area, and used the pressurized gas as a barrier in an attempt to prevent leakage across the valve/valve seat contact area. The prior art systems have not been fully successful, since the conduits have delivered the gas to the grooves over a relatively small circumferential extent, and the gas flow within the recess has not been satisfactory.
In the known prior art, the small conduits have not adequately supplied the clean gas around the entire circumference or perimeter of the valve disk. Further, since the grooves have received the clean gas having a momentum already leading towards the valve disk, the gas is not always adequately circulated within the groove to provide complete coverage of the valve disks. Also the prior system creates an air "bubble" in the groove which tends to lift the disk off the seat. Due to these features, the prior art systems have not always adequately prevented leakage.